Subject: [PATCH v2 1/3] powerpc/powernv: Always stop secondaries before reboot/shutdown

From: Nicholas Piggin <[email-masked]>
Date: Mon, 23 Oct 2017 18:05:05 +1000

Currently powernv reboot and shutdown requests just leave secondaries
to do their own things. This is undesirable because they can trigger
any number of watchdogs while waiting for reboot, but also we don't
know what else they might be doing, or they might be stuck somewhere
causing trouble.

The opal scheduled flash update code already ran into watchdog problems
due to flashing taking a long time, but it's possible for regular
reboots to trigger problems too (this is with watchdog_thresh set to 1,
but I have seen it with watchdog_thresh at the default value once too):

  reboot: Restarting system
  [  360.038896709,5] OPAL: Reboot request...
  Watchdog CPU:0 Hard LOCKUP
  Watchdog CPU:44 detected Hard LOCKUP other CPUS:16
  Watchdog CPU:16 Hard LOCKUP
  watchdog: BUG: soft lockup - CPU#16 stuck for 3s! [swapper/16:0]

So remove the special case for flash update, and unconditionally do
smp_send_stop before rebooting.

Return the CPUs to Linux stop loops rather than OPAL. The reason for
this is that the path to firmware is longer, and the CPUs may have
been interrupted from firmware, which may cause problems to re-enter
it. It's better to put them into a simple spin loop to maximize the
chance of a successful reboot.

Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/include/asm/opal.h             |  2 +-
 arch/powerpc/platforms/powernv/opal-flash.c | 28 +---------------------------
 arch/powerpc/platforms/powernv/setup.c      | 15 +++++----------
 3 files changed, 7 insertions(+), 38 deletions(-)

diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
index 04c32b08ffa1..ce58f4139ff5 100644
--- a/arch/powerpc/include/asm/opal.h
+++ b/arch/powerpc/include/asm/opal.h
@@ -317,7 +317,7 @@ struct rtc_time;
 extern unsigned long opal_get_boot_time(void);
 extern void opal_nvram_init(void);
 extern void opal_flash_update_init(void);
-extern void opal_flash_term_callback(void);
+extern void opal_flash_update_print_message(void);
 extern int opal_elog_init(void);
 extern void opal_platform_dump_init(void);
 extern void opal_sys_param_init(void);
diff --git a/arch/powerpc/platforms/powernv/opal-flash.c b/arch/powerpc/platforms/powernv/opal-flash.c
index 2fa3ac80cb4e..632871d78576 100644
--- a/arch/powerpc/platforms/powernv/opal-flash.c
+++ b/arch/powerpc/platforms/powernv/opal-flash.c
@@ -303,26 +303,9 @@ static int opal_flash_update(int op)
 	return rc;
 }
 
-/* Return CPUs to OPAL before starting FW update */
-static void flash_return_cpu(void *info)
-{
-	int cpu = smp_processor_id();
-
-	if (!cpu_online(cpu))
-		return;
-
-	/* Disable IRQ */
-	hard_irq_disable();
-
-	/* Return the CPU to OPAL */
-	opal_return_cpu();
-}
-
 /* This gets called just before system reboots */
-void opal_flash_term_callback(void)
+void opal_flash_update_print_message(void)
 {
-	struct cpumask mask;
-
 	if (update_flash_data.status != FLASH_IMG_READY)
 		return;
 
@@ -333,15 +316,6 @@ void opal_flash_term_callback(void)
 
 	/* Small delay to help getting the above message out */
 	msleep(500);
-
-	/* Return secondary CPUs to firmware */
-	cpumask_copy(&mask, cpu_online_mask);
-	cpumask_clear_cpu(smp_processor_id(), &mask);
-	if (!cpumask_empty(&mask))
-		smp_call_function_many(&mask,
-				       flash_return_cpu, NULL, false);
-	/* Hard disable interrupts */
-	hard_irq_disable();
 }
 
 /*
diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c
index b23d8beb0f1e..ff9422776a81 100644
--- a/arch/powerpc/platforms/powernv/setup.c
+++ b/arch/powerpc/platforms/powernv/setup.c
@@ -112,17 +112,12 @@ static void pnv_prepare_going_down(void)
 	 */
 	opal_event_shutdown();
 
-	/* Soft disable interrupts */
-	local_irq_disable();
+	/* Print flash update message if one is scheduled. */
+	opal_flash_update_print_message();
 
-	/*
-	 * Return secondary CPUs to firwmare if a flash update
-	 * is pending otherwise we will get all sort of error
-	 * messages about CPU being stuck etc.. This will also
-	 * have the side effect of hard disabling interrupts so
-	 * past this point, the kernel is effectively dead.
-	 */
-	opal_flash_term_callback();
+	smp_send_stop();
+
+	hard_irq_disable();
 }
 
 static void  __noreturn pnv_restart(char *cmd)
-- 
2.13.3